title: The first engagement of partners in the Euprymna scolopes-Vibrio fischeri symbiosis is a two-step process initiated by a few environmental symbiont cells.
abstract: We studied the Euprymna scolopes-Vibrio fischeri symbiosis to characterize, in vivo and in real time, the transition between the bacterial partner's free-living and symbiotic life styles. Previous studies using high inocula demonstrated that environmental V. fischeri cells aggregate during a 3 h period in host-shed mucus along the light organ's superficial ciliated epithelia. Under lower inoculum conditions, similar to the levels of symbiont cells in the environment, this interaction induces haemocyte trafficking into these tissues. Here, in experiments simulating natural conditions, microscopy revealed that at 3 h following first exposure, only ∼ 5 V. fischeri cells aggregated on the organ surface. These cells associated with host cilia and induced haemocyte trafficking. Symbiont viability was essential and mutants defective in symbiosis initiation and/or production of certain surface features, including the Mam7 protein, which is implicated in host cell attachment of V. cholerae, associated normally with host cilia. Studies with exopolysaccharide mutants, which are defective in aggregation, suggest a two-step process of V. fischeri cell engagement: association with host cilia followed by aggregation, i.e. host cell-symbiont interaction with subsequent symbiont-symbiont cell interaction. Taken together, these data provide a new model of early partner engagement, a complex model of host-symbiont interaction with exquisite sensitivity.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Altura
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Elizabeth A C
authors.initials: EA
authors.lastname: Heath-Heckman
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Amani
authors.initials: A
authors.lastname: Gillette
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Natacha
authors.initials: N
authors.lastname: Kremer
authors.affiliation: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Krachler
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Caitlin
authors.initials: C
authors.lastname: Brennan
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Ruby
authors.affiliation: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Orth
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: McFall-Ngai
mesh_terms: D048908:Aliivibrio fischeri / Q000472:pathogenicity*; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D002923:Cilia / Q000382:microbiology*; D049832:Decapodiformes / Q000382:microbiology*; D004777:Environment; D004848:Epithelium / Q000382:microbiology; D006434:Hemocytes / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000235:genetics; D008027:Light; D009092:Mucous Membrane / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000235:genetics; D013559:Symbiosis / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial